Tension regulating mechanism for differential drives



Jan. 1, 1946. H. w. BUTTERWORTH, JR., ETAL 2,392,226

TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVES Filed Aug. 4, 1945 6 Sheets-Sheet l Jan. 1, 1946. H. w. BUTTERWORTH. JR, ET AL 3 2 TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVES Filed Aug. 4, 1943 e Sheets-Sheet 2 Jan. 1, 1946. H, w. BUTTERWORTH, JR. ET AL 2,392,226

TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVES Filed Aug. 4, 1943 6 Sheets-Sheet 5 I [may 01-1152;

Jan. 1, 1946. H. w. BUTTERWORTH. JR, ETAL 2,392,226

TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVES Filed Aug. 4, 1945 6 Sheets-Sheet 4 Jan. 1, 1946. H. W. BUTTERYWORTH, JR, ET AL 2,392,226

TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVES Filed Aug. 4, 1943 6 Sheets-Sheet 5 Jan. 1, 1946. H. w. BUTTERWORTH, JR. ET AL 2,39

TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVES Filed Aug. 4, 1943 6 Sheets-Sheet 6 IIII II/I 6 0 Z? P Y j n I I I l w ornegs iwm Patented Jan. 1, 1946 TENSION REGULATING MECHANISM FOR DIFFERENTIAL DRIVE Barry W. Butter-worth, Jr., Chestnut Hill, Pa., and Winfield B. Heinz, Bound Brook, N. J.

Application August 4, 1943, Serial No; 497,384

31Claims.

This invention relates to winding and/or unwinding apparatus and more particularly to an apparatus for maintaining in a strip being wound or unwound from a roll a substantially uniform tension.

In many types of apparatus, strip or strand material is wound from one to another of a pair of arbors, as for example, in the ordinary dyeing machines. Obviously, the diameters of the rolls of material vary throughout the winding or unwinding operation with the result that it is extremely diflicult to maintain in the material anything approximating a uniform tension. In many instances, in such machines, a mandrel is provided for delivering material, the linear speed of which is fixed by an associated mechanism, this mechanism often receiving the material from one mandrel and delivering it to a second mandrel, thereby increasing the dificulty of maintaining uniform tension.

An important object of the present invention is the provision of an apparatus for maintaining a substantially uniform tension in the material.

Another object of the invention is the provision of an apparatus of this character in which, in the case of an unwinding roll or mandrel, most of the energy imparted to the unwinding roll through the material leaving it is fed back to the apparatus impelling the strip.

A further object of the invention is the provision of means for driving winding and unwinding rolls simultaneously in such manner that the linear speed and the tension of the material between the rolls will be maintained substantially constant without regard to the changing diameters of the two rolls.

A further object of the invention is the provision of apparatus of this character which may be reversed for operation in either direction at will.

A further object of the invention is the provision of means whereby the tension in material leaving an unwinding roll and passing to a winding roll and having its linear speed fixed by a separate apparatus acting thereon between the winding and unwinding rolls may have its tension between the speed controlling mechanism and both the winding and unwinding rolls maintained substantially uniform and to provide means whereby the material may be completely wound upon the winding roll.

A further and more specific object of the invention is the utilization of a well-known principle of the common differential in accomplishing the foregoing objects.

These and other objects we attain by the constructions shown in the accompanying drawings, wherein for the purpose of illustration, we have shown preferred embodiments of our invention and wherein:

Figure 1 is a diagrammatic view illustrating a simple form of our invention in which the strip is driven by nip rolls;

Figure 2 is a diagrammatic view illustrating a construction in which the mandrels are.independently driven;

Figure 3 is a modification illustrating the inclusion of means for insuring the complete winding of the strip upon the mandrel to which it is being wound when the strip is being driven by nip rolls;

Figure 4 illustrates the application of a hydraulic control in accordance with our invention;

Figures 5 and 6 are sectional views through the servomotor and controls a fluid supply element utilized in the arrangement illustrated in Figure 4; and

Figure 7 is a view similar to that of Figure l as illustrating the use of an electrical control.

Referring now to the drawings and more particularly to Figure 1, travelin strand or strip material S propelled by squeeze rolls III, II driven at constant speed in any suitable manner (not herein shown) is supplied to or withdrawn from a rotating mandrel I2, the latter condition being herein illustrated. Driving power is transmitted through suitable connections, indicated generally at 13, to one shaft 14 of a differential l 5, the cage of which is mounted for rotation, the power thus delivered being divided between the cage I6 of the differential and the second differential shaft I1. The second shaft I1 is connected with the mandrel l2 through a continuously variable transmission i8.

It is evident that shaft l3 performs only the one function of transmitting power to shaft I4 from a source of power which in Fig. 1 is the driven roll H. Any other constant-speed power source could be used instead of roll ll, subject only to the further requirement that it also be capable of absorbing power when the roll S is being unwound, under tension. When operation is in the reverse direction from that shown, and the material is being wound upon roll l2, the necessary power is transmitted from shaft l3 through the intermediate gearing to the roll I 2.

The transmission illustrated is that commonly known as the Reeves drive which comprises input and output shafts bearing pairs of cone pulleys l9 which may b1 iimultaneously oppositely adjusted to thereby provide a variation of the speed of the output shaft. This variation is at present illustrated as accomplished by simultaneous adjustment of a pair of levers 20, the ends of which are disclosed as engaging oppositely threaded nuts 2| mounted upon and coacting with threads upon the driven shaft of a control motor 22. The power received by difi'erential gear I5 is transmitted to the mandrel l2 causing it to turn if winding. If unwinding, as shown in Figure 1, the power flow is reversed and the power required to retard the unw.nding roll I2 is largely transmitted back to the driving roll ll, thus reducing the amount of power which would otherwise be required to drive it. Due to this difference in power flow, the differential case It will be driven in the same direction without regard to the direction of rotation of the mandrel l2.

Driven by the differential casing l6, as for example, by the belt and pulley arrangement, generally indicated at 23, is a pump 24 withdrawing a suitable liquid such as oil from a; reservoir 25 and returning it to this reservoir through a suitable resistance, such as orifice 26. The discharge line 21 is in communication with a suitable pressure switch, for example, as a Bourdon tube 23 controlling the direction of operation of motor 22 through a suitable switch 23. The motor 22 acting upon the controls of the transmission l8 varies the speed of rotation of the mandrel l2 so as to tighten the material S if the pressure is too low and to loosen it if the pressure is too high. Since constant pressure at the switch implies a constant torque on pump 24, this in turn implies constant torque on difi'erential cage 16. The torque on shaft II as delivered to transmission 18 must likewise be constant. The maintenance of constant pressure on discharge line 21 likewise implies constant speed of the pump 24 and of differential cage I 5. Since the speed of shaft I 4 is constant, it follows that the speed of shaft l1 must also be constant. Shaft 11- accordingly delivers to transmission l8 both constant torque and constant speed and accordingly constant power. Thus the power being delivered to or received from mandrel l2 must be constant as long as the pressure on the discharge line 21 is constant.

Since the linear speed of material S is kept constant by the constant speed of roll II, and since the power transmitted by it to or from mandrel I 2 is also substantially constant, the tension in material S must likewise be substantially constant with the exception of those slight departures which result from friction losses, and of those transient departures from perfect constancywhich are characteristic of every automatic control mechanism. These deviations will be negligible if the machine parts are of proper construction.

When material S is being wound onto mandrel l2, by means of power transmitted from roll ll through shafts l3, I4, I 1 and transmission It! to mandrel l2 (as alreadyexplained on page 1), the speed of material S is fixed as before by the constant speed of roll II. In manner identical to that described above, the power delivered to material S by way of shaft I1 is maintained substantially constant. Consequently the tension in material S must also be substantially constant.

Under certain transient conditions of operation, as for example, in threading, the transmission It! may reach one or the other of the limits of its adjustment, under which conditions, excessive pressure might be built up in discharge line 21 and to this end the discharge line is provided with a relief valve indicated at 29. A further abnormal condition which may occur during starting would result from slack material between mandrel l2 and the squeeze rolls In and II. Under such circumstances, there would be no torque on shaft 81 and the diflerential ca e [8 will rotate in a reverse direction. By providing a check valved connection between the discharge line 21 and the reservoir, as indicated at 30, the pump 24 can be permitted to rotate freely in a reverse direction and shaft l1 may be permitted to remain stationary or even to rotate in a reverse direction until the slack in the material S has been taken up. This will occur very rapidly and on its completion the mandrel l2 will begin rotating through the tension of the material which will gradually increase as the several differential gears attain their rated speeds. The supply lines to motor 22 are equipped with a reversing switch, as indicated at 3!, so that the direction of operation may be reversed depending on whether the mandrel I2 is winding or delivering material.

Under certain circumstances, it may be found that the motor 22 has a tendency to overshoot" producing too great a change in the ratio of transmission l8. In order to eliminate the resultant hunting a compensating pump 32 may be driven by the ratio changing motor 22. This pump is connected between the discharge line 21 and the reservoir in such manner that when the motor 22 is operating to cause an increase in the speed of rotation of the cage 16 and accordingly an increase in pressure in the discharge line 21, the pump 32 delivers liquid to the discharge line 21, thus creating a premature increase in pressure therein. This premature increase will open the switch 23, stopping the motor earlier than it would otherwise have been stopped. If, after stoppage of motor 22, the ratio has not yet been suficiently corrected, the motor 22 will restart and another correcting change will be commenced, this procedure continuing until the proper ratio has been attained. If, on the other hand, the motor 22 is correcting the ratio in transmission I8 to lower pressure in the discharge line 21 of pump 24, the pump 32 will tend to remove a portion of the liquid from the discharge line 21 and return it to the reservoir, thus creating a premature decrease in pressure in the discharge line 21. Reversing valves 33 and 34 are provided in the connections to pump 32 in order that the compensating action may be correctly applied without regard to whether mandrel I2 is winding or unwinding.

In Figure 2 I have illustrated application of my invention to a construction wherein strand or strip material S is unwound from one roll and wound upon a second roll, the construction being such that either of the rolls may act as the winding roll or mandrel. In the illustrated structure, rolls 35 and 36 are selectively driven by associated motors 31 and 38, each motor acting upon the roll through the output shaft 0 of constant variable transmission I81: of the type hereinbefore referred to. The output speeds of transmissions l8a are simultaneously and oppositely varied by means of control motor 22a through shaft C. The input shafts Ha, Ha of the transmissions [8a are oppositely driven by their associated motors 31 and 33, only one of which is operated during movement of the strip from one to the other of the rolls and these input shafts constitute the shafts of the differential I 511 operating the control pump 24a. The drive shaft of motor 22a operates a compensating pump 32a having associated therewith, as in Figure 1, reversing valves 33a, 34a. The control switch 3la reversing the power supply to motor 22a, in the present instance, serves likewise to select which of motors 31 or 38 is to become operative.

In the present instance, the arrows indicating the direction of motion disclose the motor 38 as being operative. When motor 31 is operated, the direction of operation is reversed, the material then winding upon the mandrel 35 and unwinding from mandrel 36. During operation in either direction, the control motor 22a simultaneously ,adjusts both transmissions i8a as is necessary to maintain constant pressure in the exhaust line 21a and accordingly constant torqueand speed on the differential cage I6a. In the present illustration the speed of shaft i4a being held constant by motor 38 and having maintained therein a constant torque by the differential, the power transmitted through it from one to the other of rolls 35 and 36 and back through the traveling material S must also be constant. Accordingly, the product of the speed and tension in material S is maintained constant.

As the radius of the roll on mandrel 36 increases, motor 22a adjusts the ratios in transmissions I8a in the direction which reduces the speed of mandrel 36 and increases the speed of mandrel 35. Thus the linear speed of the material S, which would increase as the winding roll radius increases were its rotational speed to remain unrial S from the beginning to the end of a complete pass in either direction depends upon the construction of transmissions l8a, in its eifect upon the respective rates at which their ratios are changed by rotation of motor 22a. Commercially available variable-ratio transmissions for useas units I8a provide a sufliciently close approach to constancy in linear speed throughout an entire pass to satisfy the requirements of most applications.

In the form of invention shown in Figure 3, the material S is driven by nip rolls 39 and 48 to cause unwinding of the material from a mandrel 4! or 42 and a winding of the material upon the other of these mandrels. The structure of this form of our invention is almost identical with that of the preceding structure and accordingly corresponding elements have been indicated by b primes of the ordinals employed in connection with Figure 2.

In this construction, the material S is maintained at constant speed by the driven nip rolls 39 and 40 and the power is derived from the moving material, motors 31b and 38b being utilized only in final winding of the material upon the mandrel, which is, at that time, acting as a winding roll. During normal operation the roll from -which the material is being unwound, in the present instance, roll 4!, drives through its transmission one shaft of the differential l5b, the differential dividing this power between its cage |6b and the shaft i4b, which in turn serves to drive the roll 42 upon which the material is being wound. Motor 221) simultaneously and oppositely varies the speeds of transmissions l8b through shaft D. Motors 31b and 38b are idle until the material leaves the roll 4|. During normal operation the pressure in exhaust line 21b is sufllcient to maintain switch 43 open, this switch, serving when closed, to close the circuit of the motor 31b or 38b. With the direction of operation as indicated, motor 38b would be the active motor and when the material leaves the unwinding mandrel 4|, the direction of rotation of the cage l6b will be reversed. This will result in immediate drop of pressure in exhaust line 211) with the result that switch 43 closes energizing motor 38b which will continue to operate winding the cloth upon mandrel 42 until the machine is stopped, Since stopping the machine involves opening of the circuits on motors 22b and 38b and of the motor driving rolls 39 and 40 (not shown), the control switches of these motors are preferably interlocked.

By the operations already described, shafts Nb and iii) are maintained at substantially constant speed and torque by the control mechanism. Consequently, the power transmitted from shaft llb to the differential and from the differential to shaft MD is constant. Since motors 31b and 38b are de-energized except at the extreme end of a pass, and since friction losses can be made negligible by ordinarily good construction, the power transmitted through traveling material S is also constant. Since its speed is kept fixed by the constant speed of rolls 39 and 40, it follows that the tension in material S must also be constant.

In the form of invention illustrated in Figures 4, 5 and 6, the strip S may be driven either by nip rolls'44 or by driving either of the mandrels as desired, in which case, the motors M will constitute power motors. The motors M, if driven, nip rolls 44 employed, may be utilized as the motors 31b, 38b in the construction illustrated in Figure 3. In the present construction, the control of the variable speed transmissions 45 included in the driving connections 46 between the mandrels and the gear shafts of differential 41 is through a servo-motor 48, the piston 49 of which is linked to the operating levers 50 of the transmissions 45 as at 5|.

The motor 48, shown in detail in Figure 5, is of that type in which the piston 49 assumes a position corresponding to the pressure applied to a controlling pilot valve 52. The controlling pressure is delivered below a diaphragm 53 and assuming that this pressure overcomes the bias placed on the diaphragm by a spring 54, the diaphragm 53 will be moved to the left in Figure 5 thereby admitting pressure fluid from the chamber 55 to port 56 and causing piston 49 to move to the right. This movement increases the tension of spring 54 until the excess pressure is balanced, a corresponding movement being given the operating levers 50 of transmissions 45. With a decrease in pressure in the diaphragm chamber 51, the spring 54 will move the valve to the right, thereby introducing the fluid pressure to port 58 and causing the piston to move to the left until the spring tension again equals the diaphragm pressure.

The supply of fluid for the pilot valve control is derived from a pump 59 driven by the differential cage and having its discharge line provided with an orifice return 6| to sump 62. The discharge line 63 of the pump isselectively connectable to chambers C and D of a pressure control element 64, these chambers being in turn selectively connectable with the sump through a reversing valve 65. The pressure to be controlled, at present illustrated as being derived from the discharge line 63, is admitted to an inlet chamber 66, entering a diaphragm chamber A from the inlet chamber through a ball valve 61 controlled by a stem 68 which is operatively linked at 69 to a stem 10 secured to the mutual diaphragm ll separating chambers C and D. The stem 66 has a hollow upper end portion secured to the diaphragm 12 of chamber A, the upper end of this hollow stem being sealable by the ball valve 61 and the stem below the diaphragm 12 of chamber A having a port 13.

Assuming that the pressure in chamber A is sufliciently low to permit the stem 68 to elevate, ball valve 61 will be unseated and pressure fluid will enter the chamber A. Assuming that the pressure in chamber C is suificiently high to cause a downward movement of the stem 68, the ball valve 65 will seat and thereafter the upper end i of the stem 68 will separate from the ball valve permitting pressure fiuidto drain from chamber A into chamber B, from which it will return to the sump through a drain I4. The discharge of chamber A is connected to the diaphragm chamber 51 of servo-motor 48 by conduit 15. It will be noted that the pressure derived from chamber A will always be proportional to the pressure of the discharge line 63 so that the position of piston 49 will be determined by the pressure of the exhaust line. By admitting pressure to the chamber D, the operations described above are reversed, that is to say, an increase of pressure in the chamber D will cause an increase of pressure in the chamber A. In this manner, the direction of operation of piston 49 in response to a rise or fall of pressure in the discharge line 63, is reversed.

Operating pressure from piston 49 may be derived from any suitable source, being at present shown as derived from the discharge line 16 of the second pump 11 driven by thedifferential. The discharge line 16 is returned to the sump through a pressure regulating valve Hi, this pump thus becoming a tension regulating pump maintaining a substantially uniform tension in strip S.

In Figure 7 of the drawings, we have illustrated an arrangement wherein the functions of speed and tension control have been separated. In this arrangement the transmission 19 is controlled by a motor 80, the operation of which is in turn controlled by a speed controlled switch 8| driven by the cage of differential 82. As illustrated, this switch comprises an eddy current disc 83 mounted on the drive shaft 84 of a gear pump 85 driven by the differential cage. The periphery of this disc operates between the poles of a 'permanent magnet 86 carried by a switch arm 81, the motion of which in one direction is urged by means of a spring 88. The rotation of the eddy current disc which is always in the direction of the arrows will tend to close the switch blade on contact 89 when the speed increases beyond a given rate. When the speed drops below this rate, spring 88 will close the switch on contact 90,

thus reversing the direction of operation of motor 80. In order to eliminate hunting, the magnet 86 is equipped with a modifying coil 9| supplied from a rectifier 92 through a relay 93 which operates when the circuit of motor 80 is closed. The relay 93 is a reversing relay in the direction of flow of current through coil 9| and the direction of closure is dependent upon the direction of operation of motor 80. When the speed of eddy current disc 83 is too high, this coil acts to reduce the field strength of the magnet 86 and when it is too low it acts to reenforce the field strength. The switch 8| thus acts to control the speed of the strip S at all times. Pump 85 acts to control the tension of the strip S, the discharge line 94 of the pump returning to sump 95 through an adjustable relief valve 96. The

pump thus acts to maintain a constant tension Y in the strip without regard to small fluctuations in speed of the rotation of the cage of diflerential 82.

While we have above consistently referred to the use of the cage element of the diflerential as utilized in driving the control mechanism, it will, of course, be understood that this is solely for the reason that this element is mechanically preferable and ofiers a more convenient means of connection than the remaining elements which are, however, available to this end, In other words, the roll and mandrel may be connected to any two of the three power transmitting elements of the differential and the control mechanism driven by the third element.

Since the constructions herein illustrated are merely examples of various forms which our invention may assume and since the arrangements illustrated are obviously capable of considerable modification without departing from the spirit of our invention, we do not wishto be understood as limiting ourselves thereto, except as hereinafter claimed.

We claim:

1. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual rotatable power transmitting elements,a driving connection between one of said elements and the roll, a driving connection between a second element and the mandrel including a continuously variable transmission, and means responsive to the speed of rotation of the third element varying the output speed of the transmission.

2. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a difierential gearing having the three usual rotatable power transmitting elements, a driving connection between one of said elements and the roll, a driving connection between a second element and the mandrel includin a continuously variable transmission, and means responsive to the speed of rotation of the third element varying the output speed of the transmission including a pump driven by the third element.

3. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a. differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, and means responsive to the speed of rotation of thethird element for varying the output speeds of said transmissions.

4. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, means to maintain a constant tension in the strip between said roll and mandrel comprising a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, and means responsive to the speed of rotation of the third element for simultaneously and oppositely varying the out- 76 put speeds of said transmissions.

5. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, means responsive to the speed of rotation of the third element for varying the output speeds of said transmissions. and means to selectively drive the elements con nected to the roll and mandrel.

6. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, means to maintain a constant tension in the strip between said roll and mandrel comprising a difierential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, means responsive to the speed of rotation of the third element for simultaneously and oppositely varying the output speeds of said transmissions, and means to selectively drive the elements connected to the roll and mandrel.

'7. In combination with a differential having the three usual rotatable power transmitting elements, members having driving connections with two of said elements, means for main aining within limits, not including zero, the differential speed of said two elements, including a transmission interposed between one of said members and the differential, and means for controlling the output speed of said transmission by the speed of rotation of the third element.

8. In combination with a diflerential having the three usual rotatable power transmitting elements, members havin driving connections with two of said elements, means for maintaining within limits, not including zero, the differential speed of two elements, including a transmission interposed between each of said members and the differential, and means for simultaneously and oppositely controlling the output speeds of said transmissions by the speed of rotation of the third element.

9. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a diiferential gearing having the three usual power transmitting elements, adriving connection between one of said elements and the roll, a driving connection between a second of the elements and the mandrel including a continuously variable transmission, a pump driven by the third element, and means respon- 60 sive to the pressure of the pump varying the, output speed of the transmission.

10. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip 65 from the mandrel, a differential gearing having the three usual power transmitting elements, a driving connection between one of said elements and the roll, a driving connection betwen a sec- 70 ond of the elements and the mandrel including a continuously variable transmission, a pump driven by the third element, means responsive to the pressure of the pump varying the output speed of the transmission, and means to increase 7 the pump pressure during operation 0! the Pressure responsive means.

11. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll forfeeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, a pump driven by the third element, and means responsive to the pressure of the pump for varying the output speeds of said transmissions.

12. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, a pump driven by the third element, means responsive to the pressure of the pump for varying the output speeds of said transmissions, and means to increase the pump pressure during operation of the pressure responsive means.

13. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, means to maintain a constant tension in the strip between said roll and mandrel comprising a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, a pump driven by the third element, and means responsive to the pressure of the pump for simultaneously and oppositely varying the output speeds of said transmissions.

14. In apparatus for winding and unwinding strip materials, ,a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, means to maintain a constant tension in the strip between said roll and mandrel comprising a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, a pump driven by the third element, means responsive to the pressure of the pump for simultaneously and oppositely varying the output speeds of said transmissions, and means to increase the pump pressure during operation of the pressure responsive means.

15. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a difierential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, a pump driven by I the third element, means responsive to the pressure of the pump for varying the output speeds of said transmissions, and means to selectively drive said two diiferential elements.

16. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, a pump driven by the third element, means responsive to the pressure of the pump for varying the output speeds of said transmissions, means to selectively'drive said two differential elements, and means to increase the pump pressure during operation of the pressure responsive means.

17. In apparatus for Winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a diilerential gearing having the three usual rotatable power transmitting elements, a driving connection between one of said elements and the roll, a driving connection between the other of the elements and the mandrel 7 ments, connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, and mean responsive to the speed of rotation of the third element for varying the output speeds of said transmissions, comprising a reversible electric motor and a circuit for the motor including a reversing switch controlled by said third element.

19. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, means to maintain a. constant tension in the strip between said roll and mandrel comprising a difierential gearing having the three usual rotatable power transmitting elements, driving connections between tw: of said elements and said roll and mandrel, each of said drivin connections including a continuously variable transmission, and means responsive to the speed of rotation of the third element for simultaneously and oppositely varying the output speeds of said transmissions, comprising a reversible electric motor and a circuit for the motor including a reversing switch controlled by said third element.

20. In apparatus for Winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a diilerential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said' roll and mandrel, each of said driving connections including a continuously variable transmission, means responsive to they speed of rotation of the third element for varying the output speeds of said transmissions comprising a reversible electric motor and a circuit for the motor including a reversing switch controlled by said third element, and means to selectively drive said shafts.

21. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual power transmitting elements, a driving connection between one oi said elements and the roll, a driving connection between another of the shafts and the mandrel including a continuously variable transmission, means responsive to the speed of rotation of the third element varying the output speed of the transmission, comprising a pump driven by said third element, a reversible electric motor for controlling the transmission, and a circuit for said motor including a reversing switch operated by the Pressure of the pump.

22. In apparatus for winding andunwindin strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, means responsive to the speed of rotation of the third element for varying the output speeds of said transmissions, comprising a pump driven by said third element, a reversible electric motor for controlling the transmissions, and a circuit for said motor including a reversing switch operated by the pressure of the pump,

23. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, means to maintain a constant tension in the strip between said roll and mandrel comprising a differential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a continuously variable transmission, means responsive to the speed of rotation of the third element for simultaneously and oppositely varying the output speeds of said transmissions, comprising a pump driven by said third element, a reversible electric motor for controlling the transmissions, and a circuit for said motor including a reversing switch operated by the pressure of the pump.

24. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a difi'erential gearing having the three usual rotatable power transmitting elements, driving connections between two of said elements and said roll and mandrel, each of said driving connections including a, continuously variable transmission, means responsive to the speed of rotation of the third element for varying the output speeds of said transmissions comprising a pump driven by said third element, a reversible electric motor for controlling the transmissions, a circuit for said motor includinga reversing switch operated by the pressure of the pump, and means to selectively drive said shafts.

25. In combination with a differential having the three usual rotatable power transmitting elements, members having driving connections with two of said elements, means for maintaining within limits, not including zero, the difierent speed of said two elements, including a transmission interposed between one of said members and the difl'erential, means for controlling the output speed of said transmission by the speed of rotation of the third element, comprising a pump driven by said third element, a reversible electric motor for controlling the transmission, and a circuit for said motor including a reversing switch operated by the pressure of the pump.

26. In combination with a differential having the three usual rotatable power transmitting elements, members having driving connections with two said elements, means for maintaining within limits, not including zero, the difierential speed of said two elements, including a transmission interposed between one of said members and the diflerential, means for controlling the output speed of said transmission by the speed of rotation of the third element, comprising a reversing electric motor controlling the transmission, and a circuit for the motor including a speed responsize switch driven by the third element.

27. In apparatus for winding and unwinding strip materials, a rotatable mandrel, a driven roll for feeding a strip to or withdrawing a strip from the mandrel, a difierential gearing having the three usual rotatable power transmitting elements, a driving connection between one of said elements and the roll, a driving connection between another of the elements and the mandrel including a continuously variable transmission, means responsive to the speed of rotation of the third element varying the output speed of the transmission, comprising a reversing electric motor controlling the transmission, and a circuit for the motor including a speed responsive switch driven by the third element.

28. In combination with a differential having the three usual rotatable power transmitting elements, members having driving connections with two of said elements, and automatic control means operating to maintain within limits not including zero, the differential speed between said two elements, including a transmission interposed between one of said members and the differential, and means for controlling the output speed 01 said transmission by the speed of rotation of the third element.

29, In combination with a diflerential having the three usual rotatable power transmitting elements, members having driving connections with two oi said elements, and automatic control means operating to maintain within limits not including zero, the difierential speed between said two elements, including a transmission interposed between each of said members and the diiferential, and means for simultaneously and oppositely controlling the output speeds of said transmissions by the' speed of rotation of the third element.

30. In combination with a difierential having the three usual rotatable power transmitting elements, members having driving connections with two of said elements, and automatic control means operating to maintain within limits not including zero, the differential speed between said two elements, including a transmission interposed between one of said members and the differential, means for controlling the output speed of said transmission by the speed of rota tion of the third element, comprising a pump driven by said third element, a reversible electric motor for controlling the transmission, and a circuit for said motor including a reversing switch operated by the pressure of the pump.

31. In combination with a difierential having the three usual rotatable power transmitting elements, members having driving connections with two of said elements, and automatic control means operating to maintain within limits not including zero, the differential speed between said two elements, including a transmission interposed between one of said members and the difierential, means for controlling the output speed of said transmission by the speed of rotation of the third element, comprising a reversing electric motor controlling the transmission, and a circuit for the motor including a speed responsive switch driven by the third element.

HARRY W. BUI'I'ERWORTH, JR. WINFIELD B. HEINZ. 

